DESCRIPTION: Changes in foveal color vision processing throughout the life span are now well-documented, but the factors responsible for these changes are only partially understood. The purpose of this research is to determine the optical and neural factors that contribute to age- related changes in human color vision. Senescence of foveal and parafoveal processes will be compared. Visual performance at a neural level will be quantified using corrections for light losses due to age- related changes in the ocular media and to individual variation in macular pigment density. Sensitivity of isolated cone pathways will be measured at several retinal loci, and spatio-temporal summation experiments will be conducted to identify possible changes in neural ,organization such as increased neural noise, reduction in quantum catch and changes in cell numbers and morphology. Color appearance will be quantified by measurement of unique hues. Scotopic sensitivity and spatial summation will also be tested because of losses in rod numbers with advancing age. Tests of sensitivity and color appearance will also be conducted before and after cataract extraction and implantation of intraocular lenses. These experiments will provide further evidence pertaining to neural compensation which promotes color constancy despite lenticular senescence. The research will permit an evaluation of whether macular pigment plays a protective role for the retina and whether it is the basis for some individual differences in normal aging. It will contribute to our understanding of possible neural reorganization associated with losses of photoreceptors and ganglion cells. It will also provide fundamental data describing senescence of visual processes.